Strength Characteristics of Biopolymer Treated Pond Ash

Abstract

Biopolymer is a prominent natural polymer used for stabilizing soil and industrial waste material with low environmental impacts. Pond ash is used as road embankment material because of its faster rate of consolidation, negligible post-construction settlement and low chance of liquefaction. However, it needs good soil cover as compacted ash is easily erodible and loses strength in saturated condition. In the present study, two biopolymers such as xanthan gum and gaur gum are used for stabilizing pond ash. The biopolymer content in the pond ash is varied as 0.5%, 1%, 2% and 3% by dry weight of pond ash. The compaction characteristics such as maximum dry density (MDD), optimum moisture content (OMC), shear strength parameters such as unit cohesion, angle of internal friction, and unconfined compressive strength (UCS) of the compacted pond ash and biopolymer treated pond ash are determined under partially saturated, saturated and dried conditions. From the test data it is observed that the OMC increases and MDD decreases with increase in biopolymer content. Further, the shear strength of the stabilized pond increases due to the significant enhancement in the unit cohesion of the treated pond ash, however, the effect of biopolymer is marginal on the angle of internal friction. Even in saturated condition, the treated pond ash is able to retain its strength. Microstructural analysis reveals the accumulation of biopolymer gel in the void spaces that entangle of pond ash particles in the polymer networks.